Being dead – even for centuries – is no way to avoid a harsh critique. And poor Henry VIII has had a terrible week. As serial wife-murderers go, he’s always seemed like one of the better ones to me: without him, we’d have fewer Holbein paintings, no Hampton Court, and Hilary Mantel would be short of a major character. Nonetheless, the Historical Writers Association has just named him the worst monarch in history. Not just British monarch, either: of all the rulers who ever lived all over the world (at least one of whom boasted the surname “The Impaler”), he has been declared the absolute pits.

Had the historical novelists forgotten the great monsters of ancient Rome? Nero was such a self-absorbed ninny that his inability to address the great fire of 64AD led to the phrase that is still now hurled at hopeless leaders: he fiddled while Rome burned. He arranged for the murder of his mother, Agrippina, although it was surely her single-minded determination that put him on the throne (she possessed, according to the Roman historian Tacitus, an “almost masculine despotism”).

And quite aside from that, Nero lived under the delusion that he was a superstar musician, singer and actor. He avoided eating apples, because he believed them to be bad for the voice, and would enter singing competitions, which unaccountably he always won. He also used to take part in recitals that went on for so long that women would go into labour just to get out of the theatre. Men (for whom the baby-on-the-way excuse was less effective) used to pretend to be dead so they could be carried out as corpses. That, I think we can all agree, is not the sign of a good gig.

So wedded was Nero to the idea of himself as a great musical performer that even as his principate collapsed around him, and it became clear that he would be forced to commit suicide to avoid execution, his mind was still firmly fixated on his imagined talents. His famous last words were: “Qualis artifex pereo” – “What an artist! But still I die.”

Then there are the hapless rulers, the ones who achieved so little that they really might as well not have bothered putting on a crown. George IV won an English Heritage poll in 2008 that named him Britain’s Most Useless Monarch. Laziness, profligacy and vileness to his wife propelled him to the top of the league of uselessness. Though even he might have boasted more fans than poor Galba, emperor for about 15 minutes in Rome’s Year of the Four Emperors (68-69AD). He was dismissed by Tacitus with one of the most memorably ungenerous epigrams in all historical writing as “capax imperii nisi imperasset”: capable of ruling, if he hadn’t ruled.

And as for Henry VIII’s shocking attitude towards his wives? Well, even the most femicidal aspects of his reign leave him far behind Elizabeth Bathory, who though she wasn’t a queen was at least a Hungarian countess. She was also a vampire and murderer of hundreds of women and girls. Whether or not she actually bathed in blood, as scandalised posthumous sources suggest, we can certainly chalk her up as being a poor example of the sisterhood.

But surely the title of worst ruler the world has ever known should go to Gaius Caligula, whose charming nickname (Caligula means Little Boots) does nothing to ameliorate his molten unpleasantness. He was a monstrous combination of vanity and insanity who – according to imperial biographer Suetonius – impregnated his own sister, Drusilla. As John Hurt memorably portrayed him in I, Claudius, he became convinced that the child would one day grow up to destroy him. Comparing himself to Zeus, this version of Caligula sliced open his sister. Let us refrain from mentioning what happened next, in case you’re eating. Suffice it to say, so was Caligula.

He was a world leader at being a terrible leader, managing in four short years to reveal a terrible flaw in the imperial system (if you had a crazy emperor, there was only one way to get rid of them). He came close to provoking the whole of Judaea into rebellion, by demanding they place a statue of him in their most sacred temple. And, famously, he intended to make his horse, Incitatus, a consul, showing the kind of disrespect for both elected office and the animal kingdom that we would not see again until George Galloway put on his catsuit and a nation dry-heaved.

Sadly for Caligula, he also managed to alienate Cassius Chaerea, the prefect of his own bodyguards: he teased Chaerea for perceived effeminacy, and would issue him with lascivious watchwords that the poor man would then have to repeat. Eventually, Chaerea stabbed Caligula in the neck, bringing his reign to a premature end, and allowing him to be succeeded by his uncle Claudius. The rest, as they say, is history.